Linear actuators are commonly used when a controlled linear motion is desired instead of a rotational movement. One use of linear actuators is to be able to remotely open and close windows, for example ventilation windows of green houses. Pneumatic and hydraulic actuators have been used as they are commonly linear by nature. Both pneumatic and hydraulic actuators have many disadvantages, energy efficiency being one, which is why there has for some time been a shift towards linear actuators driven by electrical motors.
To determine the position of an actuation element of a linear actuator, linear actuators are commonly provided with position sensors. Formerly rotary potentiometers were used. Due to the mechanical nature of potentiometers, they wear out, thus lowering the reliability of the linear actuators they were used in. More modern linear actuators will most likely use wear resistant technology such as semiconductor Hall-sensors that are contact-less sensors. The US patent application US 2009/0091287 describes a linear actuator making use of Hall-sensors. Unfortunately the suggested system requires that the sensors and micro processor always need to be active. Thus there seems to be room for improvement in determining a position of an actuation element of a linear actuator.